Premier Rock Forum

losthighway wrote: Sun Dec 19, 2021 3:37 pm

Dr Tony Balls wrote: Sun Dec 19, 2021 6:47 am I dont know what a master volume amp would have to do with an amp's available headroom. All a master volume does is attenuate the signal before it huts the power section. With it full up its essentially out of the circuit.

Well, you know a little more (read:a shit ton) than I do about amps. In my life of playing guitar I've pretty much always used master volume amps using the two volume knobs in relationship with each other to determine the ideal volume and saturation. I can usually get a clean signal to go louder, by only adjusting the master volume, but the few times I've toyed with an old bassman or something when it starts overdriving, then that's just it.

Isn't the input volume attenuating the signal hitting the preamp section, and buying me headroom? Or am I perhaps using the term 'master volume amp' all wrong?
I say this not as an argument, but in genuine curiosity.

Both "volume" and "master" controls generally just serve to attenuate or turn-down the signal before going to the following stage. They also are essentially out of the circuit when all the way up, so just having a master doesnt affect the overall headroom that would be there if you didnt have the master control.

The basic chronology is that historically the volume control was early in the signal path and didnt operate too differently from the volume knob on the guitar. When you turned that all the way up you got awesome sounding distorted tone but at very high volumes because you were overdriving the stages downstream. So people tried to figure out ways to let the amp get distorted and then turn down the signal before it got too loud. I.e. where can we add a second volume control further down the signal path to achieve this result. The rub, though, is that you're generating distortion and sonic characteristics at every amp stage so people for ages have been trying to figure out the best, furthest-down-the-line, place to put a master control and still achieve full AC/DC at a reasonable volume and the answer is asymptotical - you can approach but never meet full AC/DC at a reasonable volume level.

I really like the one with the cannabis rex speaker in it. They're selling a sonic blue one with that speaker right now that I've got my eye on. Standard speaker is fine too although a bit more icepicky.

Dr Tony Balls wrote: Mon Dec 20, 2021 9:49 am people for ages have been trying to figure out the best, furthest-down-the-line, place to put a master control and still achieve full AC/DC at a reasonable volume and the answer is asymptotical - you can approach but never meet full AC/DC at a reasonable volume level.

^^^^^
I love this explanation.

Dr Tony Balls wrote: Mon Dec 20, 2021 9:49 am
Both "volume" and "master" controls generally just serve to attenuate or turn-down the signal before going to the following stage. They also are essentially out of the circuit when all the way up, so just having a master doesnt affect the overall headroom that would be there if you didnt have the master control.

So is it wrong to say that the input volume is buying you headroom through attenuation (even if headroom is ultimately whatever the amp's gain characteristics are with everything on full)?

Dr Tony Balls wrote: Mon Dec 20, 2021 9:49 am So people tried to figure out ways to let the amp get distorted and then turn down the signal before it got too loud. I.e. where can we add a second volume control further down the signal path to achieve this result.

I suppose this is why the boutique amp companies boast of 'post phase-inverter master volume circuit', which seems a way to get the volume attenuated at the latest possible stage in a circuit, so the guts can all work their mojo.

losthighway wrote: Mon Dec 20, 2021 7:26 pm

Dr Tony Balls wrote: Mon Dec 20, 2021 9:49 am
Both "volume" and "master" controls generally just serve to attenuate or turn-down the signal before going to the following stage. They also are essentially out of the circuit when all the way up, so just having a master doesnt affect the overall headroom that would be there if you didnt have the master control.

So is it wrong to say that the input volume is buying you headroom through attenuation (even if headroom is ultimately whatever the amp's gain characteristics are with everything on full)?

Yeah I suppose you could think of it that way.

losthighway wrote: Mon Dec 20, 2021 7:26 pm

Dr Tony Balls wrote: Mon Dec 20, 2021 9:49 am So people tried to figure out ways to let the amp get distorted and then turn down the signal before it got too loud. I.e. where can we add a second volume control further down the signal path to achieve this result.

I suppose this is why the boutique amp companies boast of 'post phase-inverter master volume circuit', which seems a way to get the volume attenuated at the latest possible stage in a circuit, so the guts can all work their mojo.

Yep. The only older design that I know of that used a post phase-inverter master volume was the Orange OD series in the late 70s. They were just Orange OR amps with a master volume. Most big brands then and now use a pre-phase inverter one for reasons that are a mystery to me (likely cost, somehow). Even in the post-PI world there are three main types, as documented by Ken Fischer, and some are better than others, though that's up for debate. I have my favorite one for sure.

The 'even-later' in the circuit option is a speaker attenuator. After the output transformer!

I have no need for one of these, but I'm smitten with this color variation of it. It's like the wildberry Pop-Tart!

four_oclocker_2.2 wrote: Tue Dec 21, 2021 9:24 am I have no need for one of these, but I'm smitten with this color variation of it. It's like the wildberry Pop-Tart!

HARD AGREE

four_oclocker_2.2 wrote: Tue Dec 21, 2021 9:24 am I have no need for one of these, but I'm smitten with this color variation of it. It's like the wildberry Pop-Tart!

Oh man! $100 extra but I might have to get that!

Honestly, considering the upgraded speaker it comes with, it isn't THAT much of a price difference.

Maybe I should just pick one of these up...

I think Tim/Andy owns one of these, and saw Andy play through it w/ Mint Mile once. Sounded great, because Andy (and he was playing a newer Danelectro into it), and for one of his solos he just went over and turned the amp up, then turned it back down when it was over.